Open loop multiple access for WLAN

ABSTRACT

In a method for transmitting information in a wireless local area network (WLAN), a plurality of different data streams corresponding to a plurality of different devices are orthogonally multiplexed onto a single symbol stream without using channel state information corresponding to a plurality of channels between a transmitting device and the plurality of different devices. One or more transmit streams are generated using the single symbol stream.

CROSS-REFERENCE TO RELATED APPLICATION

This disclosure claims the benefit of U.S. Provisional PatentApplication No. 61/174,930, entitled “Open Loop SDMA, and itsApplications in WLAN,” which was filed on May 1, 2009, the entiredisclosure of which is hereby incorporated by reference herein.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication networks and,more particularly, to wireless local area networks.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

When operating in an infrastructure mode, wireless local area networks(WLANs) typically include an access point (AP) and one or more clientdevices. WLANs have evolved rapidly over the past decade. Development ofWLAN standards such as the Institute for Electrical and ElectronicsEngineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n Standards hasimproved single-user peak data throughput. For example, the IEEE 802.11bStandard specifies a single-user peak throughput of 11 megabits persecond (Mbps), the IEEE 802.11a and 802.11g Standards specify asingle-user peak throughput of 54 Mbps, and the IEEE 802.11n Standardspecifies a single-user peak throughput of 600 Mbps.

These WLANs operate in either a unicast mode or a multicast mode. In theunicast mode, the AP transmits information to one client device at atime. In the multicast mode, the same information is transmitted to agroup of client devices concurrently.

SUMMARY

In one embodiment, a method for transmitting information in a wirelesslocal area network (WLAN) includes orthogonally multiplexing a pluralityof different data streams corresponding to a plurality of differentdevices onto a single symbol stream without using channel stateinformation corresponding to a plurality of channels between atransmitting device and the plurality of different devices. The methodalso includes generating one or more transmit streams using the singlesymbol stream.

In other embodiments, the method may include one or more of thefollowing features. The method also includes transmitting the one ormore transmit streams via a single carrier in at least one physicallayer data unit, wherein each of the at last one physical layer dataunit includes data from each of the different data streams modulated onthe single carrier. The single carrier is a sub channel in an orthogonalfrequency domain multiplexing (OFDM) signal. Orthogonally multiplexingthe plurality of different data streams corresponding to the pluralityof different devices onto the single symbol stream comprises utilizing aspace time block code. Orthogonally multiplexing the plurality ofdifferent data streams corresponding to the plurality of differentdevices onto the single symbol stream comprises utilizing the Alamouticode to multiplex two different data streams corresponding to twodifferent devices onto the single symbol stream. The method furtherincludes transmitting to the plurality of devices data that indicates,for each of the plurality of devices, a corresponding ordering of datafor the device on the single symbol stream. Orthogonally multiplexingthe plurality of different data streams corresponding to the pluralityof different devices onto the single symbol stream comprises mappingbits corresponding to at least two different data streams into a singlequadrature amplitude modulation (QAM) constellation point. The methodfurther includes transmitting to the plurality of devices data thatindicates, for each of the plurality of devices, how one or more bitsfor the device are mapped to the QAM constellation point. Orthogonallymultiplexing the plurality of different data streams corresponding tothe plurality of different devices onto the single symbol streamcomprises interleaving symbols corresponding to the plurality ofdifferent data streams in the single symbol stream. The method furtherincludes transmitting to the plurality of devices data that indicates,for each of the plurality of devices, how data for the device isinterleaved in the single transmit stream. Orthogonally multiplexing theplurality of different data streams corresponding to the plurality ofdifferent devices onto the single symbol stream comprises forming aplurality of media access control (MAC) layer protocol data units(MPDUs), each MPDU having a respective MAC header, wherein data for eachdevice is included in a respective MPDU. At least a first physical layerdata unit includes a plurality of MPDUs corresponding to differentdevices. The method further includes transmitting to the plurality ofdevices data that indicates the first physical layer data unit includesmultiple MPDUs corresponding to different devices. The data thatindicates the first physical layer data unit includes multiple MPDUscorresponding to different devices is included in a header of the firstphysical layer data unit.

In another embodiment, an apparatus comprises a wireless local areanetwork (WLAN) physical layer (PHY) unit. The PHY unit is configured toorthogonally multiplex a plurality of different data streamscorresponding to a plurality of different devices onto a single symbolstream without using channel state information corresponding to aplurality of channels between a transmitting device and the plurality ofdifferent devices. The PHY unit is also configured to generate one ormore transmit streams using the single symbol stream.

In yet another embodiment, a method includes receiving a physical layerdata unit that includes a plurality of different data streamscorresponding to a plurality of different devices orthogonallymultiplexed onto a single symbol stream without using channel stateinformation corresponding to a plurality of channels between atransmitting device and the plurality of different devices. The methodalso includes receiving data that indicates how one data streamcorresponding to one of the plurality of different devices isorthogonally multiplexed onto the single symbol stream, and utilizingthe data that indicates how the one data stream is multiplexed onto thesingle symbol stream to decode data corresponding to one of theplurality of different devices in the physical layer data unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a block diagram of an example wireless local area network (WLAN)10, according to an embodiment;

FIG. 2 is a block diagram of an example subsystem of a networkinterface, according to an embodiment;

FIG. 3 is a block diagram of an example physical layer (PHY) unit,according to an embodiment;

FIG. 4 is a block diagram of an example orthogonal space time block codeunit, according to an embodiment;

FIG. 5 is a flow diagram of an example method for multiplexing symbolscorresponding to different data streams onto a plurality of spatialstreams, according to another embodiment;

FIG. 6A is a block diagram of another example orthogonal space timeblock code unit, according to an embodiment;

FIG. 6B is a block diagram of another example orthogonal space timeblock code unit, according to an embodiment;

FIG. 7 is a flow diagram of another example method for multiplexingsymbols corresponding to different data streams onto a plurality ofspatial streams, according to another embodiment;

FIG. 8 is a block diagram of another example PHY unit, according to anembodiment;

FIG. 9 is a flow diagram of an example method for mapping datacorresponding to a plurality of data streams onto a single constellationpoint, according to an embodiment;

FIG. 10 is a block diagram of an example constellation mapper, accordingto an embodiment;

FIG. 11 is a flow diagram of an example method for multiplexing symbolscorresponding to a plurality of data streams onto a single symbolstream, according to an embodiment;

FIG. 12A is a diagram of an example PHY data unit, according to anembodiment;

FIG. 12B is a diagram of another example PHY data unit, according to anembodiment;

FIG. 13 is a block diagram of another example subsystem of a networkinterface, according to an embodiment; and

FIG. 14 is a diagram illustrating the transmission of a downlink dataunit followed by a plurality of acknowledgments from different devices,according to an embodiment.

DETAILED DESCRIPTION

In embodiments described below, a wireless network device such as anaccess point (AP) of a wireless local area network (WLAN) transmitsindependent data streams to multiple client devices simultaneously. Inparticular, the wireless device orthogonally multiplexes data for themultiple clients onto a single symbol stream without using channel stateinformation (CSI), and then transmits the multiplexed data (e.g., usingorthogonal frequency division multiplexing (OFDM)). Similarly, inembodiments described below, a device that receives such an orthogonallymultiplexed signal retrieves data intended for the device usingknowledge of how the independent data streams were orthogonallymultiplexed. In at least some embodiments, because multiplexing of thedata for multiple clients is done without using CSI, such multiplexingdoes not require CSI feedback (i.e., open loop multiplexing) andtherefore overhead is reduced.

FIG. 1 is a block diagram of an example wireless local area network(WLAN) 10, according to an embodiment. An AP 14 includes a hostprocessor 15 coupled to a network interface 16. The network interface 16includes a medium access control (MAC) unit 18 and a physical layer(PHY) unit 20. The PHY unit 20 includes a plurality of transceivers 21,and the transceivers are coupled to a plurality of antennas 24. Althoughthree transceivers 21 and three antennas 24 are illustrated in FIG. 1,the AP 14 can include different numbers (e.g., 1, 2, 4, 5, etc.) oftransceivers 21 and antennas 24 in other embodiments. In an embodiment,the AP 14 is configured to orthogonally multiplex data for multipledevices onto a single symbol stream without using CSI, and then transmitthe multiplexed data (e.g., using OFDM) to the multiple client devices.

The WLAN 10 includes a plurality of client devices 25. Although fourclient devices 25 are illustrated in FIG. 1, the WLAN 10 can includedifferent numbers (e.g., 1, 2, 3, 5, 6, etc.) of client devices 25 invarious scenarios and embodiments. Two or more of the client devices 25are configured to receive signals transmitted by the AP 14 on whichindependent data for the two or more client devices 25 is orthogonallymultiplexed, and each such configured device 25 retrieves data from thesingle transmit stream that is intended for the client device 25.

A client device 25-1 includes a host processor 26 coupled to a networkinterface 27. The network interface 27 includes a MAC unit 28 and a PHYunit 29. The PHY unit 29 includes a plurality of transceivers 30, andthe transceivers are coupled to a plurality of antennas 34. Althoughthree transceivers 30 and three antennas 34 are illustrated in FIG. 1,the client device 25-1 can include different numbers (e.g., 1, 2, 4, 5,etc.) of transceivers 30 and antennas 34 in other embodiments. In anembodiment, the PHY unit 29 is configured to retrieve data for theclient device 25-1 from multiplexed data for multiple client devices 25.

In an embodiment, one or both of the client devices 25-2 and 25-3 has astructure the same as or similar to the client device 25-1. In theseembodiments, the client devices 25 structured like the client device25-1 have the same or a different number of transceivers and antennas.For example, the client device 25-2 has only two transceivers and twoantennas, according to an embodiment.

According to an embodiment, the client device 25-4 is a device (e.g., alegacy client device) that is not enabled to retrieve data for theclient device 25-4 from multiplexed data for multiple client devices 25.

According to the IEEE 802.11a and the IEEE 802.11n Standards, differentdevices share the communication channel by utilizing a carrier sense,multiple access (CSMA) protocol. Generally speaking, CSMA, according tothe IEEE 802.11a and the IEEE 802.11n Standards, specifies that a devicethat wishes to transmit should first check whether another device in theWLAN is already transmitting. If another device is transmitting, thedevice should wait for a time period and then again check again to seewhether the communication channel is being used. If a device detectsthat the communication channel is not being used, the device thentransmits using the channel. With CSMA, in other words, data that is fora particular device (i.e., not multicast data) can only be transmittedon the channel when no other data is being transmitted on the channel.

According to an embodiment, the AP 14 is enabled to transmit differentdata streams to different client devices 25 at the same time. Inparticular, the PHY unit 20 is configured to orthogonally multiplex datafor multiple client devices 25 onto a single symbol stream without usingCSI. One or more transmit signals are generated using the single symbolstream.

FIG. 2 is a block diagram of an example subsystem 100 of a networkinterface that may be utilized in the network interface 16, according toan embodiment. The subsystem 100 is configured to orthogonally multiplexdata for multiple client devices onto a single spatial stream withoutusing CSI.

A plurality of media access control (MAC) sub-units 104-1 correspondingto different client devices (sometimes referred to herein as “users”)provide independent data streams (i.e., the streams include differentdata) to a PHY unit 108. The PHY unit 108 is configured to orthogonallymultiplex data for multiple client devices onto a single spatial streamwithout using CSI, and to generate one or more transmit signals usingthe single spatial stream. In some embodiments, the single spatialstream is one of a plurality of spatial streams generated by the PHYunit 108, and the PHY unit 108 also orthogonally multiplexes data forthe multiple client devices on the one or more other spatial streams. Inthese embodiments, the PHY unit 108 generates the one or more transmitsignals also using the one or more other spatial streams. The one ormore transmit signals are provided to a transceiver (not shown) fortransmission via one or more transmit antennas (not shown), according toan embodiment.

The PHY unit 108 includes a preamble generator 112 to generate apreamble of a PHY data unit. The preamble of the PHY data unit includesinformation that indicates whether the PHY data unit was generated usingone or more spatial streams on each of which data for multiple clientdevices is orthogonally multiplexed. For example, a bit or set of bitsin the preamble may indicate whether the PHY data unit was generatedusing one or more spatial streams on each of which data for multipleclient devices is orthogonally multiplexed.

FIG. 3 is a block diagram of an example PHY unit 150 that is utilized asthe PHY unit 108 of FIG. 2, in an embodiment. The PHY unit 150receives 1) independent data streams corresponding to n users. Aplurality of encoders 154 separately encode each of then user datastreams using one or more suitable forward error correction codes. Aplurality of constellation mappers 108 separately map sets of one ormore bits to constellation points (e.g., QAM constellation points)corresponding to a plurality of OFDM sub-channels to generate separatesymbol streams corresponding to then user data streams.

An orthogonal space-time-block-coding (O-STBC) unit 162 orthogonallymultiplexes symbols from the outputs of the constellation mappers 108onto a plurality of STBC encoded spatial streams such that each of atleast two of the output spatial streams of the O-STBC unit 162 includesdata from multiple constellation mappers 158. In one embodiment, thenumber of output streams of the O-STBC unit 162 equals the number n userdata streams.

A spatial mapping unit 166 maps the output streams of the O-STBC unit162 into N_(TX) transmit symbol streams. A plurality of inverse discreteFourier transform units 170 receives the N_(TX) transmit symbol streamsand generates N_(TX) transmit signals. In embodiments or scenarios inwhich spatial mapping is not utilized, the spatial mapping unit 166 doesnot apply spatial mapping and/or is omitted. In embodiments or scenariosin which spatial mapping is not utilized, the N_(TX) transmit symbolstreams are merely the spatial stream outputs of the O-STBC unit 162.

FIG. 4 is a block diagram illustrating an example O-STBC unit 180 thatis utilized as the O-STBC unit 162 of FIG. 3, according to anembodiment. In particular, the O-STBC unit 180 is utilized in scenariosin which the number n of user data streams is two. The O-STBC unit 180receives symbols from two constellation mappers 108-1 and 108-2 andapplies the Alamouti code to generate two output streams. For example,if the output of the constellation mapper 108-1 for an OFDM sub-channelis a constellation point x₁, and the output of the constellation mapper108-2 for an OFDM sub-channel is a constellation point x₂, then theO-STBC unit 180 generates:

$A = \begin{bmatrix}x_{1} & x_{2} \\{- x_{2}^{*}} & x_{1}^{*}\end{bmatrix}$where the first column of A corresponds to a sub-channel in a first OFDMsymbol, the second column of A corresponds to the sub-channel in asecond OFDM symbol after the first OFDM symbol, the first row of Acorresponds to a first spatial stream output of the O-STBC unit 180, andthe second row of A corresponds to a second spatial stream output of theO-STBC unit 180.

Symbols from both of the constellation mappers 158 are multiplexed ontoeach output stream of the O-STBC unit 180, and each output stream of theO-STBC unit 180 includes symbols from each of the constellation mappers158. In an embodiment utilizing OFDM, the transmission of x₁ and x₂require two OFDM symbols.

In other embodiments, different orthogonal STBC codes than the Alamouticode are applied. For example, if the number of n of user data streamsis three, a suitable STBC code that generates three output spatialstreams is utilized. In another embodiment, if the number of n of userdata streams is a 2M, then M O-STBC units 180 are utilized to generate2M spatial streams.

More generally, if the number of n of user data streams is three ormore, other suitable STBC codes are utilized. For real valuedconstellation points, full data rate as a single data stream continuoustransmission can be achieved. On the other hand, for complex valuedconstellation points, the maximum data rate is lower than the full datarate if the number of spatial streams output by the O-STBC unit isgreater than two. In an embodiment, for n user data streams, theeffective rate is

$\frac{1}{n}$multiplied by the rate of a single user data stream utilizing STBC. Forexample, if there are two users, the effective data is ½ the rate of asingle user utilizing STBC.

A receiver that receives a signal encoded using an O-STBC unit such asthe O-STBC unit 162 of FIG. 3 and/or the O-STBC unit 180 of FIG. 4 canrecover the data intended for the receiver using an STBC decoder. Thereceiver should know the ordering of its own symbols in the streams.After STBC decoding and recovery of symbols intended for the receiver,the receiver then performs demodulation and FEC decoding.

FIG. 5 is a block diagram of an example method 190 for orthogonallymultiplexing a plurality symbol streams corresponding to a plurality ofdifferent client devices. In an embodiment, the method 190 isimplemented by the O-STBC unit 162 of FIG. 3 and/or the example O-STBCunit 180 of FIG. 4. In other embodiments, the method 190 is implementedby another suitable O-STBC unit. FIG. 5 is discussed with reference toFIG. 4 for ease of explanation.

At block 194, a plurality of symbol streams corresponding to differentclient devices are received. For example, the plurality of symbolstreams may correspond to the output of constellation mappers 158.

At block 196, an orthogonal STBC is utilized to multiplex the pluralityof symbol streams onto a plurality of STBC encoded spatial streams suchthat each of at least two of the spatial streams includes data frommultiple symbol streams received at block 194. In one embodiment, thenumber of output spatial streams of the O-STBC unit 162 equals a numbern of symbol streams received at block 194.

FIG. 6A is a block diagram illustrating another example O-STBC unit 210that is utilized as the O-STBC unit 162 of FIG. 3, according to anotherembodiment. In particular, the O-STBC unit 210 is utilized in scenariosin which the number n of user data streams is two. The O-STBC unit 210includes two STBC encoders 214 and a multiplexer 218. The STBC unit214-1 receives symbols from the constellation mapper 108-1 and appliesthe Alamouti code to generate two output streams. Similarly, the STBCunit 214-1 receives symbols from the constellation mapper 108-2 andapplies the Alamouti code to generate two output streams.

For example, if two successive outputs of the constellation mapper 108-1for an OFDM sub-channel are constellation points x_(1,1) and x_(1,2),then the STBC unit 214-1 generates:

$A_{1} = \begin{bmatrix}x_{1,1} & x_{1,2} \\{- x_{1,2}^{*}} & x_{1,1}^{*}\end{bmatrix}$where the first column of A₁ corresponds to a sub-channel in a firstOFDM symbol, the second column of A₁ corresponds to the sub-channel in asecond OFDM symbol after the first OFDM symbol, the first row of A₁corresponds to a first spatial stream output of the STBC unit 214-1, andthe second row of A₁ corresponds to a second spatial stream output ofthe STBC unit 214-1.

If two successive outputs of the constellation mapper 108-2 for an OFDMsub-channel are constellation points x_(2,1) and x_(2,2), then the STBCunit 214-2 generates:

$A_{2} = \begin{bmatrix}x_{2,1} & x_{2,2} \\{- x_{2,2}^{*}} & x_{2,1}^{*}\end{bmatrix}$where the first column of A₂ corresponds to a sub-channel in a firstOFDM symbol, the second column of A₂ corresponds to the sub-channel in asecond OFDM symbol after the first OFDM symbol, the first row of A₂corresponds to a first spatial stream output of the STBC unit 214-2, andthe second row of A₂ corresponds to a second spatial stream output ofthe STBC unit 214-2.

The multiplexer 218 multiplexes the outputs of the STBC units 214. Inparticular, the matrix A₁ is output by the multiplexer 218 and then thematrix A₂ is output by the multiplexer 218.

FIG. 6B is a block diagram illustrating another example O-STBC unit 230that is utilized as the O-STBC unit 162 of FIG. 3, according to anotherembodiment. In particular, the O-STBC unit 230 is utilized in scenariosin which the number n of user data streams is two. The O-STBC unit 230is similar to the O-STBC unit 210 of FIG. 6A, and includes the two STBCencoders 214 and a multiplexer 234.

The multiplexer 234 multiplexes the outputs of the STBC units 214. Inparticular, the first column of matrix A₁ is output by the multiplexer218, and then the first column of matrix A₂ is output by the multiplexer218. Next, the second column of matrix A₁ is output by the multiplexer218, and then the second column of matrix A₂ is output by themultiplexer 218.

In other embodiments, O-STBC units similar to those in FIGS. 6A and/or6B are utilized, but different STBC codes than the Alamouti code areapplied. For example, if the number of n of user data streams is three,a suitable STBC code that generates three output spatial streams isutilized. Additionally, a different suitable multiplexer is utilized. Inanother embodiment, if the number of n of user data streams is a 2M,then M O-STBC units 210 and/or 230 are utilized to generate 2M spatialstreams.

A receiver that receives a signal encoded using an O-STBC unit such asthe O-STBC unit 162 of FIG. 3, the O-STBC unit 210 of FIG. 6A, and/orthe O-STBC unit 210 of FIG. 6B can recover the data intended for thereceiver using an STBC decoder. The receiver should know the ordering ofits own symbols in the streams. After STBC decoding and recovery ofsymbols intended for the receiver, the receiver than performsdemodulation and FEC decoding.

FIG. 7 is a block diagram of an example method 260 for orthogonallymultiplexing a plurality symbol streams corresponding to a plurality ofdifferent client devices. In an embodiment, the method 260 isimplemented by the O-STBC unit 162 of FIG. 3, the example O-STBC unit210 of FIG. 6A, and/or the example O-STBC unit 230 of FIG. 6B. In otherembodiments, the method 260 is implemented by another suitable O-STBCunit. FIG. 7 is discussed with reference to FIGS. 6A and 6B for ease ofexplanation.

At block 264, a plurality of symbol streams corresponding to differentclient devices are received. For example, the plurality of symbolstreams may correspond to the output of constellation mappers 158.

At block 268, a respective set of spatial streams is generated from eachconstellation mapper 158 using STBC. For example, in FIGS. 6A and 6B,the STBC encoder 214-1 generates a set of spatial streams (e.g., A₁)using the output of the constellation mapper 158-1, and the STBC encoder214-2 generates a set of spatial streams (e.g., A₂) using the output ofthe constellation mapper 158-2.

At block 272, the spatial streams of the STBC encoders 214 aremultiplexed onto a set of output spatial streams such that each of atleast two of the output spatial streams includes data from multiplesymbol streams received at block 264. In two particular embodiments, thespatial streams of the STBC encoders 214 are multiplexed as describedabove with respect to FIGS. 6A and 6B.

The methods and apparatus described with respect to FIGS. 2-7 areutilized with other multiple access schemes, in some embodiments. Forexample, in various embodiments, one or more methods and apparatusdescribed with respect to FIGS. 2-7 are combined with orthogonalfrequency division multiple access (OFDMA) techniques described in U.S.patent application Ser. No. 12/730,651, entitled “OFDMA with Block ToneAssignment for WLAN,” filed on Mar. 24, 2010, which is herebyincorporated herein in its entirety. For instance, in one embodiment, anAP utilizes a method and/or apparatus described with respect to one ormore of FIGS. 2-7 to transmit data to a plurality of different devicesin a first OFDM sub-channel block, whereas the AP simultaneouslytransmits data to only a single device in a second OFDM sub-channelblock, i.e., the transmissions in the first and second OFDM sub-channelblocks overlap in time. In one embodiment, the transmissions in thefirst and second OFDM sub-channel blocks begin at the same time.

As another example, in various embodiments, one or more methods andapparatus described with respect to FIGS. 2-7 are utilized incombination with simultaneous downlink transmission (SDT) techniquesdescribed in U.S. patent application Ser. No. 12/175,526, entitled“Access Point with Simultaneous Downlink Transmission of IndependentData for Multiple Client Devices,” filed on Jul. 18, 2008, which ishereby incorporated herein in its entirety. For instance, in oneembodiment, an AP utilizes a method and/or apparatus described withrespect to one or more of FIGS. 2-7 to transmit data to a first group ofdevices, whereas the AP utilizes SDT (also referred to as closed-loopsimultaneous downlink multiple access (closed-loop SDMA)) to transmitdata to a second group of devices. In this embodiment, the AP utilizes afirst steering matrix to transmit data to the first group of devices,whereas the AP utilizes a set of second steering matrices to transmitdata to the second group of devices. Each steering matrix in the set ofsecond steering matrices is configured so that interference with otherdevices in the second group of devices and interference with devices inthe first group of devices is avoided. In this embodiment, data istransmitted to the first group of users in a single PHY data unit (i.e.,the single PHY data unit includes data for all devices in the firstgroup of users), and the first steering matrix is configured to so thatinterference with devices in the second group of devices is avoided.Separate steering matrices for each of the devices in the first group ofdevices is not utilized for reducing interference between devices in thefirst group of devices because the orthogonal multiplexing techniquesdescribed above minimize interference between devices in the first groupof devices.

FIG. 8 is a block diagram of another example PHY unit 300 that isutilized as the PHY unit 108 of FIG. 2, in an embodiment. The PHY unit300 includes some of the same like-numbered elements as the PHY unit 150of FIG. 3. The PHY unit 300 receives n independent data streamscorresponding to n users. The plurality of encoders 154 separatelyencode each of the n user data streams using one or more suitableforward error correction codes. An orthogonal constellation mapper 304maps sets of one or more bits from each of the n user data streams toconstellation points (e.g., QAM constellation points) corresponding to aplurality of OFDM sub-channels to generate one or more symbol streams.The orthogonal constellation mapper 304 orthogonally multiplexes datafrom the n user data streams onto the one or more symbol streams suchthat each of at least one of the output symbol streams of the orthogonalconstellation mapper 304 includes data from multiple user data streams.In one embodiment, the orthogonal constellation mapper 304 maps a set ofbits that includes at least one bit from each of the n independent datastreams to 2^(N) possible constellation points, and generates a singlesymbol stream. In another embodiment, the orthogonal constellationmapper 304 maps a first set of bits that includes at least one bit fromeach of a first set of the n independent data streams to 2^(N) possibleconstellation points, and generates a first symbol stream. In thisembodiment, the orthogonal constellation mapper 304 maps a second set ofbits that includes at least one bit from each of a second set of the nindependent data streams to 2^(N) possible constellation points, andgenerates a second symbol stream.

A space-time-block-coding (STBC) unit 308 applies a suitable STBC codeto the one or more outputs of the constellation mapper 304 to generate aplurality of STBC encoded spatial streams. Suitable STBC codes appliedby the STBC unit 308 include STBC codes currently known to those ofordinary skill in the art. In embodiments or scenarios in which STBCcoding is not utilized, the STBC unit 308 does not apply an STBC codeand/or is omitted.

The spatial mapping unit 166 maps the output streams of the STBC unit308 into N_(TX) transmit symbol streams. The plurality of inversediscrete Fourier transform units 170 receives the N_(TX) transmit symbolstreams and generates N_(TX) transmit signals. In embodiments orscenarios in which spatial mapping is not utilized, the spatial mappingunit 166 does not apply spatial mapping and/or is omitted. Inembodiments or scenarios in which spatial mapping is not utilized, theN_(TX) transmit symbol streams are merely the spatial stream outputs ofthe STBC unit 308 (or the outputs of the orthogonal constellation mapper304 if the STBC unit 308 is not utilized).

In some embodiments, the orthogonal constellation mapper 304 maps N bitsof data to 2^(N) possible constellation points in a 2-dimensional signal(e.g., QAM modulation having an in-phase (I) and a quadrature (Q)component). In these embodiments, N/2 bits determine one of the 2^(N/2)possible values of I, and the other N/2 bits determine one of the2^(N/2) possible values of Q. In one embodiment, N/N_(S) bits for eachof N_(S) client devices are utilized together to map to a QAMconstellation point. Any suitable mapping technique for mapping N/N_(S)bits of each of N_(S) client devices into a single constellation pointin a set of 2^(N) possible constellation points can be utilized. Forexample, in one embodiment, N/N_(S) bits for each of N_(S) clientdevices are aggregated in a defined manner into a set of N bits (sothat, at the client devices, each client device knows how to recoverbits intended for that client device). Then, the set of N bits is mappedto one of 2^(N) QAM constellation points in a defined manner (so that,at the client devices, each client device knows how to recover bitsintended for that client device). In this embodiment, the data rate toeach client device is effectively 1/N_(S) times the rate of a singleuser transmission.

In one specific embodiment in which N_(S) is two, N/2 bits for a firstclient device are mapped to N/2 possible I values, and N/2 bits for asecond client device are mapped to N/2 possible Q values. In thisembodiment, the data rate to each client device is effectively ½-th therate of a single user transmission.

In some embodiments, two or more orthogonal constellation mappers 304separately orthogonally map data streams to constellation points. Forexample, in one embodiment in which N_(S) is four, a first constellationmapper maps N/2 bits for a first client device to N/2 possible I values,and maps N/2 bits for a second client device to N/2 possible Q values togenerate a first symbol stream. In this embodiment, a secondconstellation mapper maps N/2 bits for a third client device to N/2possible I values, and maps N/2 bits for a fourth client device to N/2possible Q values to generate a second symbol stream.

FIG. 9 is a flow diagram of an example method 320 for orthogonallymultiplexing a plurality data streams corresponding to a plurality ofdifferent client devices. In an embodiment, the method 320 isimplemented by the orthogonal constellation mapping unit 304 of FIG. 8.FIG. 9 is discussed with reference to FIG. 8 for ease of explanation.

At block 324, a plurality of data streams corresponding to N_(S)different client devices are received. For example, the plurality ofdata streams may correspond to the output of the encoders 154.

At block 328, an orthogonal constellation mapper is utilized to map datafrom multiple data streams received at block 324 onto a singleconstellation point to generate a symbol stream. In an embodiment, atleast one bit from each data stream received at block 324 is mapped ontoa single constellation point. In an embodiment, the constellation mapper304 maps into 2^(N) possible QAM constellation points and generates asingle symbol stream. In one specific embodiment in which N_(S) is two,N/2 bits for a first client device are mapped to N/2 possible I values,and N/2 bits for a second client device are mapped to N/2 possible Qvalues. In another embodiment, two or more constellation mappersseparately map data from multiple data streams into respectiveconstellation points and generate two or more symbol streams.

FIG. 10 is a block diagram of an example orthogonal constellation mapper350 that may be utilized as or included in the orthogonal constellationmapper 304 of FIG. 8, according to another embodiment. The orthogonalconstellation mapper 350 is for orthogonally mapping two user datastreams into a single symbol stream. In other embodiments, a similarorthogonal constellation mapper 350 maps three or more user data streamsinto a single symbol stream. Additionally, in some embodiments, multipleorthogonal constellation mappers 350 can be utilized to separately mapuser data streams into a plurality of symbol streams.

The orthogonal constellation mapper 350 includes two constellationmappers 158. The constellation mapper 158-1 maps a first client datastream to constellation points to generate a first symbol stream (S₁).The constellation mapper 158-2 maps a second client data stream toconstellation points to generate a second symbol stream (S₂). Amultiplexer 354 multiplexes symbols from the constellation mapper 158-1and the constellation mapper 158-2 onto a single symbol stream. In thisway, the single symbol stream includes data from both the first clientdata stream and the second client data stream.

With the embodiment of FIG. 10, the data rate to each client device iseffectively 1/N_(S) times the rate of a single user transmission. WhenN_(S) is two, the data rate to each client device is effectively ½-ththe rate of a single user transmission. In OFDM systems, constellationmapping is applied to all sub-carriers corresponding to each of the userdevices. Thus, different OFDM symbols correspond to data for differentclient devices. For example, in a first OFDM symbol, constellationpoints corresponding to a first client device are transmitted. In asecond OFDM symbol, constellation points corresponding to a secondclient device are transmitted, and so on.

FIG. 11 is a flow diagram of an example method 370 for orthogonallymultiplexing a plurality symbol streams corresponding to a plurality ofdifferent client devices. In an embodiment, the method 370 isimplemented by the orthogonal constellation mapping unit 304 of FIG. 8and/or the orthogonal constellation mapping unit 350 of FIG. 10.

At block 374, a plurality of data streams corresponding to N_(S)different client devices are received. For example, the plurality ofdata streams may correspond to the output of the encoders 154 (FIG. 8).

At block 378, each data stream is separately mapped to constellationpoints to generate a plurality of separate symbol streams. At block 382,the plurality of separate symbol streams are mapped to a single symbolstream.

A receiver that receives a signal encoded using an orthogonalconstellation mapping unit such as the an orthogonal constellationmapping unit 304 of FIG. 8 and/or the an orthogonal constellationmapping unit 350 of FIG. 10 can recover the data intended for thereceiver using a suitable demodulator unit that, using knowledge of theordering of its own symbols in one or more symbol streams and/or knowinghow data of the device is mapped to constellation points. Afterdemodulation, the receiver performs FEC decoding to recover the userdata.

With OFDM systems, the methods and apparatus described with respect toFIGS. 8-11 are applied across all sub-channels, in some embodiments. Inother OFDM embodiments, the methods and apparatus described with respectto FIGS. 8-11 are applied across all some of the sub-channels. In someembodiments, the methods and apparatus described with respect to FIGS.8-11 are utilized in combination with multiple-input, multiple-output(MIMO) techniques.

The methods and apparatus described with respect to FIGS. 8-11 areutilized with other multiple access schemes, in some embodiments. Forexample, in various embodiments, one or more methods and apparatusdescribed with respect to FIGS. 8-11 are combined with OFDMA techniquesdescribed in U.S. patent application Ser. No. 12/730,651. For instance,in one embodiment, an AP utilizes a method and/or apparatus describedwith respect to one or more of FIGS. 8-11 to transmit data to aplurality of different devices in a first OFDM sub-channel block,whereas the AP simultaneously transmits data to only a single device ina second OFDM sub-channel block, i.e., the transmissions in the firstand second OFDM sub-channel blocks overlap in time. In one embodiment,the transmissions in the first and second OFDM sub-channel blocks beginat the same time.

As another example, in various embodiments, one or more methods andapparatus described with respect to FIGS. 8-11 are utilized incombination with SDT techniques described in U.S. patent applicationSer. No. 12/175,526. For instance, in one embodiment, an AP utilizes amethod and/or apparatus described with respect to one or more of FIGS.8-11 to transmit data to a first group of devices, whereas the APutilizes SDT (also referred to as closed-loop SDMA) to transmit data toa second group of devices. In this embodiment, the AP utilizes a firststeering matrix to transmit data to the first group of devices, whereasthe AP utilizes a set of second steering matrices to transmit data tothe second group of devices. Each steering matrix in the set of secondsteering matrices is configured so that interference with other devicesin the second group of devices and interference with devices in thefirst group of devices is avoided. In this embodiment, data istransmitted to the first group of users in a single PHY data unit (i.e.,the single PHY data unit includes data for all devices in the firstgroup of users), and the first steering matrix is configured to so thatinterference with devices in the second group of devices is avoided.Separate steering matrices for each of the devices in the first group ofdevices is not utilized for reducing interference between devices in thefirst group of devices because the orthogonal multiplexing techniquesdescribed with respect to FIGS. 8-11 minimize interference betweendevices in the first group of devices.

As discussed above with reference to FIGS. 1-11, orthogonallymultiplexed data corresponding to multiple client devices can betransmitted in a single PHY data unit. In some embodiments, the PHY dataunit formats the same as or similar to PHY data unit formats specifiedin the IEEE 802.11n Standard are utilized. FIG. 12A is a diagram of anexample PHY data unit format 400 that can be used for mixed-modetransmissions in a WLAN. With the example format 400, an orthogonalmultiplexing technique such as described above with reference to FIGS.1-11 is applied to each sub-channel in an OFDM system, according to someembodiments.

The PHY data unit 400 includes a preamble having a portion 404 thatincludes a field to indicate whether a data portion 408 includesorthogonally multiplexed data corresponding to multiple client devices,according to an embodiment.

FIG. 12B is a diagram of an example PHY data unit format 450 that can beused for Green Field transmissions in a WLAN. With the example format460, an orthogonal multiplexing technique such as described above withreference to FIGS. 1-11 is applied to each sub-channel in an OFDMsystem, according to some embodiments.

The PHY data unit 450 includes a preamble having a portion 454 thatincludes a field to indicate whether a data portion 458 includesorthogonally multiplexed data corresponding to multiple client devices,according to an embodiment.

With the PHY data unit formats 400 and/or 450, a single modulationcoding scheme (MCS) is utilized to transmit the data portion 408/458,according to an embodiment. In an embodiment, the single MCS is selectedbased on the worst channel among the channels corresponding to theplurality of client devices. In an embodiment, MAC level signaling isutilized to inform the different client devices of the ordering oforthogonal STBC or multiplexed symbols, and/or the mapping scheme formapping different client data to constellation points in the dataportion 408/458, depending on the particular embodiment. In anotherembodiment, the preamble omits the field that indicates whether the dataportion 408/458 includes orthogonally multiplexed data corresponding tomultiple client devices. For example, MAC level signaling may beutilized to signal that a PHY data unit with orthogonally multiplexeddata for different client devices will be subsequently transmitted.

FIG. 13 is a block diagram of an example subsystem 500 of a networkinterface that may be utilized in the network interface 16, according toan embodiment. The subsystem 500 is configured to orthogonally multiplexdata for multiple client devices onto a single spatial stream withoutusing CSI.

A MAC unit 504 generates separate MAC protocol data units (MPDUs)corresponding to different client devices and aggregates the MPDUs intoan aggregated MPDU (A-MPDU) using an A-MPDU generator 508. Thus, theA-MPDU generated by the MAC unit 504 includes data from independent datastreams (i.e., the streams include different data) corresponding to thedifferent client devices. For example, different MPDUs in the A-MPDUhave different MAC addresses corresponding to the different clientdevices. The MAC unit 504 also generates a signal that indicates whetherthe A-MPDU includes MPDUs for different client devices, in anembodiment.

The A-MPDU and the signal that indicates that the A-MPDU includes MPDUsfor different client devices are provided to a PHY unit 512. The PHYunit 512 generates a PHY data unit that includes the A-MPDU. Because theA-MPDU includes different MPDUs having different MAC addresses, in anembodiment, and thus the client devices can discern data intended forthemselves, the different client data in the PHY data unit isorthogonally multiplexed without using CSI.

The PHY unit 512 includes a preamble generator 516, according to anembodiment. The preamble generator 516 receives the indicator signalfrom the MAC unit 504 and sets an indicator field in a preamble of thePHY data unit to indicate that the PHY data unit includes an A-MPDU thatincludes different MPDUs for different client devices. In anotherembodiment, the preamble generator 516 does not set such an indicatorfield in the preamble of the PHY data unit. In this embodiment, MAClevel signaling may be utilized to signal that a PHY data unit withorthogonally multiplexed data for different client devices will besubsequently transmitted.

The methods and apparatus described with respect to FIG. 13 are utilizedwith other multiple access schemes, in some embodiments. For example, invarious embodiments, one or more methods and apparatus described withrespect to FIG. 13 are combined with OFDMA techniques described in U.S.patent application Ser. No. 12/730,651. For instance, in one embodiment,an AP utilizes a method and/or apparatus described with respect to FIG.13 to transmit data to a first plurality of different devices in a firstOFDM sub-channel block, and the AP simultaneously utilizes a methodand/or apparatus described with respect to FIG. 13 to transmit data to asecond plurality of different devices in a second OFDM sub-channelblock, i.e., the transmissions in the first and second OFDM sub-channelblocks overlap in time. In one embodiment, the transmissions in thefirst and second OFDM sub-channel blocks begin at the same time.

As another example, in various embodiments, one or more methods andapparatus described with respect to FIG. 13 are utilized in combinationwith SDT techniques described in U.S. patent application Ser. No.12/175,526. For instance, in one embodiment, an AP utilizes a methodand/or apparatus described with respect to FIG. 13 to transmit data to afirst group of devices, whereas the AP utilizes SDT (also referred to asclosed-loop SDMA) to transmit data to a second group of devices. In thisembodiment, the AP utilizes a first steering matrix to transmit data tothe first group of devices, whereas the AP utilizes a set of secondsteering matrices to transmit data to the second group of devices. Eachsteering matrix in the set of second steering matrices is configured sothat interference with other devices in the second group of devices andinterference with devices in the first group of devices is avoided. Inthis embodiment, data is transmitted to the first group of users in asingle PHY data unit (i.e., the single PHY data unit includes data forall devices in the first group of users), and the first steering matrixis configured to so that interference with devices in the second groupof devices is avoided. Separate steering matrices for each of thedevices in the first group of devices is not utilized for reducinginterference between devices in the first group of devices because theorthogonal multiplexing techniques described with respect to FIG. 13minimize interference between devices in the first group of devices.

In any of the embodiments described above with respect to FIGS. 1-13,the different client devices to which data was transmitted usingorthogonal multiplexing will respond to the AP with acknowledgments(ACKs) or negative acknowledgments (NACKs). Referring again to FIG. 1,in one embodiment, the MAC unit 18 of the AP schedules ACK/NACKs for thedifferent client devices 25 to which orthogonally multiplexed data istransmitted in a single PHY data unit. In this embodiment, the MAC unit18 causes indications of the times at which each client can transmit anACK/NACK to be transmitted to the client devices.

FIG. 14 is a timing diagram illustrating a reserved time interval fordownlink SDMA. A plurality of time slots after the end of the downlinkPHY data unit 550 are reserved for client devices to transmit ACK/NACKs554.

At least some of the various blocks, operations, and techniquesdescribed above may be implemented utilizing hardware, a processorexecuting firmware instructions, a processor executing softwareinstructions, or any combination thereof. When implemented utilizing aprocessor executing software or firmware instructions, the software orfirmware instructions may be stored in any computer readable memory suchas on a magnetic disk, an optical disk, or other storage medium, in aRAM or ROM or flash memory, processor, hard disk drive, optical diskdrive, tape drive, etc. Likewise, the software or firmware instructionsmay be delivered to a user or a system via any known or desired deliverymethod including, for example, on a computer readable disk or othertransportable computer storage mechanism or via communication media.Communication media typically embodies computer readable instructions,data structures, program modules or other data in a modulated datasignal such as a carrier wave or other transport mechanism. The term“modulated data signal” means a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia includes wired media such as a wired network or direct-wiredconnection, and wireless media such as acoustic, radio frequency,infrared and other wireless media. Thus, the software or firmwareinstructions may be delivered to a user or a system via a communicationchannel such as a telephone line, a DSL line, a cable television line, afiber optics line, a wireless communication channel, the Internet, etc.(which are viewed as being the same as or interchangeable with providingsuch software via a transportable storage medium). The software orfirmware instructions may include machine readable instructions that,when executed by the processor, cause the processor to perform variousacts.

When implemented in hardware, the hardware may comprise one or more ofdiscrete components, an integrated circuit, an application-specificintegrated circuit (ASIC), etc.

While the present invention has been described with reference tospecific examples, which are intended to be illustrative only and not tobe limiting of the invention, changes, additions and/or deletions may bemade to the disclosed embodiments without departing from the scope ofthe invention.

What is claimed is:
 1. A method for transmitting information in awireless local area network (WLAN), the method comprising: orthogonallymultiplexing a plurality of different individual symbol streamscorresponding to a plurality of different devices onto a single combinedsymbol stream, without using channel state information corresponding toa plurality of channels between a transmitting device and the pluralityof different devices, so that every symbol of every individual symbolstream is included in the single combined symbol stream; and generatingone or more transmit streams using the single combined symbol stream. 2.A method according to claim 1, further comprising transmitting the oneor more transmit streams via a single carrier in at least one physicallayer data unit, wherein each of the at last one physical layer dataunit includes data from each of the different individual symbol streamsmodulated on the single carrier.
 3. A method according to claim 2,wherein the single carrier is a sub-channel in an orthogonal frequencydomain multiplexing (OFDM) signal.
 4. A method according to claim 1,wherein orthogonally multiplexing the plurality of different individualsymbol streams corresponding to the plurality of different devices ontothe single combined symbol stream comprises utilizing a space time blockcode.
 5. A method according to claim 4, wherein orthogonallymultiplexing the plurality of different individual symbol streamscorresponding to the plurality of different devices onto the singlecombined symbol stream comprises utilizing the Alamouti code tomultiplex two different individual symbol streams corresponding to twodifferent devices onto the single combined symbol stream.
 6. A methodaccording to claim 4, further comprising transmitting to the pluralityof devices data that indicates, for each device of the plurality ofdevices, a corresponding ordering of data for the device on the singlecombined symbol stream.
 7. A method according to claim 1, whereinorthogonally multiplexing the plurality of different individual symbolstreams corresponding to the plurality of different devices onto thesingle combined symbol stream comprises mapping bits corresponding to atleast two different individual symbol streams into a single quadratureamplitude modulation (QAM) constellation point.
 8. A method according toclaim 7, further comprising transmitting to the plurality of devicesdata that indicates, for each device of the plurality of devices, howone or more bits for the device are mapped to the QAM constellationpoint.
 9. A method according to claim 1, wherein orthogonallymultiplexing the plurality of different individual symbol streamscorresponding to the plurality of different devices onto the singlecombined symbol stream comprises interleaving symbols corresponding tothe plurality of different individual symbol streams in the singlesymbol stream.
 10. A method according to claim 1, further comprisingtransmitting to the plurality of devices data that indicates, for eachdevice of the plurality of devices, how data for the device isinterleaved in the single transmit stream.
 11. A method according toclaim 1, wherein orthogonally multiplexing the plurality of differentindividual symbol streams corresponding to the plurality of differentdevices onto the single combined symbol stream comprises forming aplurality of media access control (MAC) layer protocol data units(MPDUs), each MPDU having a respective MAC header, wherein data for eachdevice is included in a respective MPDU, wherein at least a firstphysical layer data unit includes a plurality of MPDUs corresponding todifferent devices.
 12. A method according to claim 11, furthercomprising transmitting to the plurality of devices data that indicatesthe first physical layer data unit includes multiple MPDUs correspondingto different devices.
 13. A method according to claim 12, wherein thedata that indicates the first physical layer data unit includes multipleMPDUs corresponding to different devices is included in a header of thefirst physical layer data unit.
 14. An apparatus, comprising: a wirelesslocal area network (WLAN) physical layer (PHY) unit configured toorthogonally multiplex a plurality of different individual symbolstreams corresponding to a plurality of different devices onto a singlecombined symbol stream, without using channel state informationcorresponding to a plurality of channels between a transmitting deviceand the plurality of different devices, so that every symbol of everyindividual symbol stream is included in the single combined symbolstream, and generate one or more transmit streams using the singlecombined symbol stream.
 15. An apparatus according to claim 14, whereinthe PHY unit is configured to include data from each of the differentindividual symbol streams modulated on a single carrier in a single PHYdata unit.
 16. An apparatus according to claim 14, wherein the PHY unitincludes a space time block code unit to orthogonally multiplex theplurality of different individual symbol streams corresponding to theplurality of different devices onto the single combined symbol stream.17. An apparatus according to claim 14, wherein the PHY unit includes aconstellation mapping unit to map bits corresponding to at least twodifferent individual symbol streams into a single constellation point.18. An apparatus according to claim 17, further comprising a mediaaccess control unit configured to cause data to be transmitted to theplurality of devices to indicate, for each device of the plurality ofdevices, how one or more bits for the device are mapped to theconstellation point.
 19. An apparatus according to claim 14, wherein thePHY unit includes: a plurality of constellation mapping units togenerate at least two symbol streams using at least two differentindividual symbol streams corresponding to the plurality of differentdevices; and a multiplexer to multiplex the at least two symbol streamsonto the single combined symbol stream.
 20. A method, comprising:receiving a physical layer data unit that includes a plurality ofdifferent individual symbol streams corresponding to a plurality ofdifferent devices orthogonally multiplexed onto a single combined symbolstream, without using channel state information corresponding to aplurality of channels between a transmitting device and the plurality ofdifferent devices, so that every symbol of every individual symbolstream is included in the single combined symbol stream; receiving datathat indicates how one individual symbol stream corresponding to one ofthe plurality of different devices is orthogonally multiplexed onto thesingle combined symbol stream; and utilizing the data that indicates howthe one individual symbol stream is multiplexed onto the single combinedsymbol stream to decode data corresponding to one of the plurality ofdifferent devices in the physical layer data unit.